For navigation applications in a set of fixed pictures or videos, it is useful to be able to display all the pictures or videos at a single glance. For this purpose, it is interesting to generate a reduced size version of each fixed picture or each picture of the videos so that said pictures or videos are displayed simultaneously on a same screen and are able to be compared easily. Likewise, for a broadcast application of a video content on a mobile device having a small sized screen, e.g. on a mobile phone or on a PDA, it is necessary to generate a reduced size version of each picture of the video in order to display them on the small sized screen.
A method known to a person skilled the art to generate these reduced pictures or videos from a source picture or video consists in subsampling said source picture or video. In the case of a significant reduction in size some picture parts are unusable by the user as they are too small.
Cropping a part of the picture containing the most salient or visually attractive areas of the picture is another method. However, in the presence of multiple faces in the picture, such method often fails to define an appropriate cropping window in the picture.